Hack saw blade



Patented May 1 7, 1932 UNITED STATES PATENT OFFICE HOWARD M. GERMAN, OFGRAFTON, PENNSYLVANIA, ASSIGNOB TO UNIVERSAL STEEL COMPANY, OFBRIDGEVILLE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA mcx saw BLADENo Drawing.

The present invention relatesto hack saw saw blades of my prior Patent1,616,364 of I February 1, 1927.

In my prior patent I described an improved hardened steel hack saw bladecontaining embedded nodules of coalesced cementite of a size sufiicientto serve as abrasive grains, together with a-' process ofannealing andhardening whereby such metallic structure could be roduced. In my priorpatent I described tlie process as applied to usual hack saw steels, andalso to an improved hack sawsteel described in said patent whichdiffered from the usual hack saw steels in containing tungstenpreferably from about 2% to 5%, and chromium preferably from about .50%to 2.50%.

While the hack saw blades made in accordance with my prior patent hadconsiderably better wearing qualities than the usual hack'saw blades, 1have found it possible to about double the wearing qualities of my priorpatented hack saw blades by chang-.

ing the proportions of the alloying elements. The chromium is increasedmaterially over the chromium in my prior patent. The tungsten is alsopreferably increased. Pref: erably a small amount of vanadium is addedto the alloy.-

The following are two typical analyses of hack saw steels embodying mypresent invention:

I Per cent Carb n 1. 03 Manganese .30 Silicon 30 Tungst n 3.05Chromium..- 7.80 Vanadium- .40 Sulphur Not over 04. Phosphorus N'ot overPer cent Carbon 84 Manganese 40 Silicon .25 Tungsten- 7.95 Chromi m Y 7.03 Vanadi J Application nled July 11, 1929. Serial No. 377,806.

Per cent Sulphur Not over .04 Phosphorus Not over .04

The hack saw steels of the compositions herein set forth may be meltedin the usual steel making furnaces, such as electric or cruciblefurnaces, cast in ingots, and rolled into sheets. The hack saw bladesare made from the sheets in accordance with the process set forth in myprior Patent 1,616,364, which may be briefly summarized as follows:

The sheets are given an annealing treatment at about 1425 to 147 5Fahrenheit, being held at this temperature for about eighteen hours andthen allowed to cool slowly in the furnace. ment causes the coalescenceof the free ce- This special annealing treatmentite or carbides intosmall nodules or spheroids of a size suflicient to serve as abra-' sivegrains in the finished saw blade. The

sheets are 'cut and formed into the hack saw blades which are hardenedby heating them just above the critical point and then quickly quenchingin oil. The blades are afterward drawn or tempered to toughen them.

The hack saw blades as thus made have the and tougher and more resistantto softening,

under the frictional heat of use.

Thehack saw-blades, as made of the steels described above have aboutdouble the wearing qualities of the hack saw blades made of the steeldescribed in my prior patent. The

chromium and tungsten 'bothtend to form carbides which go-into thecoalesced cementite nodules and make the nodules somewhat harder andlarger. Some of the chromium and tungsten carbides also go into solutionin the matrix and -make it structurally stronger and stiffer, aswell asraising the softening point of the matrix so that the matrix will resistsoftening under the fric tional heat to which the hack saw is subjectedin use. This is important because under the frictional heat of use ofthe hack saw the matrix tends to become softened and to lose thestructural strength requisite to properly supportthe abrasive nodulesand cementite. Apparently the increased amount'of chromium and tungstencarbides in the nodules themselves increases the ability of the nodulesto resist disintegration under the frictional heat of use. The increasein the chromium content also seems to make the abrasive nodules not onlylarger and harder, but also more numerous.

The vanadium, which is preferably added, tends to make the freecementite nodules more stable and resistant to disintegration under theheat incident to the work of the saw. The

-vanadium enters both the nodules and the 7 .cementite containing thealloying meta s or as f their carbides in combination with the ironcarbide, Such free cementite is often referred .to as carbides or freecarbides.

The proportions of the alloyin metals may be varied from the specificana yses set forth above. For example, the carbon may vary from-about.70% to 1.30%,preferably from about .80% to 1.10%. The increase in thechromium and tungsten permits the carbonto be somewhat lowered from theranges set forth in my prior patent, thus tending to increase thetoughness of the steel.

The chromium is higher than that set forth in my prior patent, being inexcess of 3% but not over about 12%, preferably from about 6% to 9%, andusually about 7% t0'8%.

The tungsten may be within the ranges set forth in my prior patent, butpreferably averages somewhat hlgher. The tungsten may vary from about 2%to 12%, preferably. from about 2% to 10%, and usually from about3%to8%..

The steel also preferably has 'a small vanadium addition. The vanadiummay vary from an effective amount up to about 3%,

' preferably from about-20% to'.50%.-

The manganese, silicon, sulphur and phosphorus may vary within the usualranges for steels of this character and as set forth in my prior patent,the manganese being preferably about .20% to .50%, the siliconpreferably ,jabout .15 to .30%, and the sulphur and phccilsphoru'spreferably not over about 01% ea v 1 I have also found that the additionof vanadium also improves the hack saw blades made in accordance withthe process and steels described in my said prior patent, since thevanadium tends to render the carbide nodules more stable and to toughenthe matrix.

ferred embodiments of my invention, it is to be understood that theinvention-is not 'so limited, but may be otherwise embodied within thescope of the following claims.

I claim:

1. A hardened steel hack saw blade containin chromium in excess of 3%but not over aiout 12% and tungsten about 2% to 12%, and containingembedded abrasive nodules of cementite.

2. A hardened steel hack saw blade containin chromium about 6% to 9% andtung- While I have specifically described the presten a out 3% to 8%,and containing embedded abrasive nodules of cementite. 3. A hardenedsteel hack saw blade containing chromium about 7% to 8% and tungstenabout 3% to 8%, and containing embedded abrasive nodules of cementite.

4. A hardened steel hack saw blade containin chromium in excess of 3%but not over a out 12%, tungsten from about 2% to 12% and an effectiveamount of vanadium up to about 3%, and containing embedded abrasivenodules of cementite.

5. A hardened steel hack saw blade con- 7 taining chromium about 6% to9%, tungsten about 2% to 10% and vanadium about 20% to .50%, andcontaining embedded abrasive nodules of cementite.

6. A hardened steel hack. saw blade con ta-ining embedded nodules'ofcoalesced cementite of a size sufficient to serve as abrasive grains,and containing an effective amountof vanadium up to about 3%. 7. Ahardened steel hack saw blade containing embedded nodules of coalescedcementite of a size sufficient to serve as abrasive grains, andcontaining about .20% to 50% vanadium.

8. As an intermediate product in the .man-

ufacture of steel hack saw blades, an annealed steel sheet containingchromium in excess of 3% but not over about 12%. and tungsten about 2%to 12%, and containing embedded abrasive nodules of cementite.

9. As an intermediate product in the manufacture of steel hack sawblades, an annealed steel sheet containing chromium about 6% to 9%andtungsten about 3% to 8%, v 'and containing embedded abrasive nodulesof cementite. v

10. As an intermediate product .in the manufacture of steel hack sawblades, an annealed steel sheet containing chromium about 7% to 8% andtungsten about 3% to 8%, and containing embedded abrasive nodules ofcementite. 1

esa-10a 11; As an intermediate roduotin the manufacture of steel backsaw lades, an annealed steel sheet containing chromium in excess of 3%but not over about 12%, tungsten from 5 about 2% to 12% and an effectiveamount of vanadium up to about 3%; and containing embedded abrasivenodules of cementite.

12. As an intermediate roduct in the manufacture of steel hack sawbladeaan annealed steel sheet containing chromium about 6% to 9%,tungsten about 2% to 10% and vanadium about 20% to .50%, and containingembedded abrasive nodules of oementite. V

13. As an intermediate 1;)roduct in the manufacture of steel hack sawlades, an annealed steel sheet containin embedded nodules of coalescedcementite o a size suflicient to serve as abrasive grains, andcontaining an effectiv amount of vanadium up to about 3%. 14. As anintermediate roduct in themanufacture of steel hack saw lades' anannealed steel sheet containin embedded nodules of" coalesced cementiteo a size suificient to serve as abrasive grains, and containing about20% to .50% vanadium.

15. A hardened steel hack saw blade co taining embedded nodules ofcoalesced eementite of a size suflicient to serve as abrasive grains,and containing. about 20% to 3% vanadium.

16. As an intermediate roductin the man- 7 ufacture of steel back sawlades, an annealed steel sheet containing. chromium about 7% to v 12%and tungsten about 2% to 12%,and con- 5 taining embedded abrasivenodules of ce-l mentite. v d d Intestimony whereof I havehereunto set imy hand.

' HOWARD M.

